The invention relates generally to wellhead systems for use with oil and gas wells. In particular, the invention relates to a wellhead system having a tubular hanger that is securable to a wellhead.
A typical oil and/or gas well utilizes strings of casing that are supported from a casing hanger that is, in turn, supported by a wellhead assembly. The strings of casing serve many purposes. For example, casing strings may be used to define the wellbore at various stages of drilling to keep formation fluids out of the wellbore and drilling mud in the wellbore.
Thermal changes in the casing string may produce forces that drive the casing string to lengthen or shorten. For example, if the well is shut-in, warm production fluid will not flow through the well. This allows the casing string to be cooled down by its surroundings. For example, seawater may cool down the wellhead and casing in a subsea well. This cooling may produce thermal contraction of the casing string. Conversely, when a flow of production fluid is initiated, the warm temperature of the production fluid may produce thermal expansion of the casing string.
Oil and/or gas, typically, are produced from the wellbore via production tubing, rather than from a casing string. The production tubing is supported from a tubing hanger. The location of the tubing hanger in a wellhead is important to enable an external device to be coupled to the tubing hanger. Typically, a tubing hanger is supported by a casing hanger disposed within a wellhead. However, as noted above, thermal forces may cause the casing string to expand or contract, thus causing the position of the tubing hanger to vary.
As a result, there is a need for a technique that addresses some or all of the problems described above. The techniques described below may address one or more problems described above.